* This classification of tarsal coalitions is based on age, articular involvement and secondary arthritic changes. The classification may be used as a foundation for the discussion of surgical management.

Offering insights from the literature as well as clinical experience, this author discusses conservative modalities, reviews important considerations for choosing an optimal surgical procedure and shares pearls on resection and arthrodesis options.

A tarsal coalition exists when an abnormal union causes restricted motion or absence of motion between two or more tarsal bones. Tarsal coalitions often produce a dramatic symptom complex, which one may ultimately identify as rigid peroneal spastic flatfoot.

Three clinical findings in the midfoot and/or rearfoot — pain, limitation of motion and muscle spasm — should make the clinician suspect a tarsal coalition. Additionally, prolonged pain after a simple ankle sprain or injury in an adolescent or young adult as well as a lack of response to treatment should make one suspicious for a tarsal coalition.

One ultimately diagnoses a tarsal coalition through a combination of the characteristic symptom complex, clinical acumen and radiographs. Physicians may also consult advanced imaging studies such as computed tomography (CT) scans, magnetic resonance imaging (MRI) or both.

After one establishes the diagnosis, the treatment can focus on reducing symptomatology and restoring as much function as feasible. It is rare for the treatment of a tarsal coalition to fully restore normal foot function. Therefore, an improvement in the patient’s quality of life is the primary goal of any treatment plan.1

A Closer Look At Effective Conservative Treatments

A tarsal coalition may be asymptomatic and an incidental finding on routine radiographs or an advanced diagnostic imaging study. In a study of 23 patients with tarsal coalition, Jack found that five patients (22 percent) had no symptoms.2 If an asymptomatic tarsal coalition is present, no treatment is mandated. However, one should counsel the patient regarding the finding and the potential need for treatment should the coalition result in future symptomatology.

When a tarsal coalition becomes symptomatic, it does not necessarily remain symptomatic. For a symptomatic coalition, one should generally initiate conservative treatment directed toward restriction of subtalar and midtarsal joint motion. This results in a reduction of pain and muscle spasm. One may combine this approach with anti-inflammatory medication and physical therapy as needed.

Shoe modifications, padding, orthotic devices or casting may adequately limit subtalar and midtarsal joint motion. Shoe modifications may include a Thomas heel, a medial heel wedge or a longer medial heel counter. Padding in the shoe may include a heel wedge or a medial longitudinal support.

One should specifically construct orthoses to limit subtalar joint motion. A neutral position device with a long rearfoot post or an orthotic device posted in valgus may prove to be beneficial. University of California Biomechanics Lab (UCBL)-type orthoses with high medial and lateral flanges may also be helpful. If these fail or if the patient has significant symptoms, consider a soft cast, strapping, cast boot or a below knee walking cast.3 If desired, one may apply these devices after a local corticosteroid injection to the area of the coalition.

Apply the below knee cast or cast boot with the ankle and subtalar joints in their neutral positions and keep this intact for three to six weeks. In more severe cases or if initial immobilization fails, one may attempt to apply a non–weightbearing cast. If this approach is going to be effective in this situation, more than one trial of immobilization may be necessary to attempt to render the patient free of symptoms.4,5

Studies have reported that casting produces symptomatic improvement in approximately 25 to 33 percent of patients.6,7 However, although symptoms may resolve with a course of immobilization and offloading, the symptoms may recur at any time in the future and may necessitate repeated immobilization and offloading, or surgical intervention.

Essential Considerations In Choosing A Surgical Procedure

Surgical treatment is essentially limited to either resection of the coalition or fusion of the involved joint complex. However, significant debate continues in regard to the indications and timing for the procedures, and the results to be expected with these two diverse surgical approaches. For this reason, I have proposed a classification system, which may be a framework for the construction of an appropriate treatment plan.8,9

While the Articular Classification System is not all inclusive, it does consider several important parameters used in the development of any treatment regimen. These parameters include patient age, articular involvement and the extent of secondary adaptive or arthritic changes. Since the introduction of the Articular Classification System over 20 years ago, I now advocate that one routinely consider the size of the coalition when developing a surgical treatment plan, especially with talocalcaneal coalitions.

Patient age is consistently a factor when one plans the surgical treatment of a tarsal coalition. Ideally, in all patients, the surgeon would like to resect the tarsal coalition and restore normal or nearly normal function to the involved tarsal joints. From a practical standpoint though, this is often not possible. The surgeon must balance the likelihood of success of resection of the coalition against the possible need for additional surgery (i.e., arthrodesing procedures) should this resection procedure fail.

In the juvenile patient who has not yet attained osseous maturity (i.e., open physeal growth plates), resection is favored for most tarsal coalitions. The remodeling potential of the growing juvenile patient is significant. For example, a child or adolescent is much more likely than an adult to achieve an acceptable subjective and objective return of function after a severe joint depression calcaneal fracture. Similarly, in the juvenile patient with a tarsal coalition, one anticipates that the increased joint motion achieved with resection of the coalition in combination with continued osseous growth and remodeling will result in a more normal, less painful midfoot and rearfoot joint complex. If symptoms and limited function remain or recur in this immature patient after resection, one can perform major arthrodesis procedures at a later date (i.e., after osseous maturity occurs).

When it comes to adult patients, surgeons may also consider resection of a tarsal coalition but this approach is more likely to fail. The reality of limited remodeling potential in the adult patient diminishes the probability of recovery to a reasonably functional, symptom free state. Therefore, mature patients who undergo coalition resection are at a greater risk for recurrent or increased joint limitation, and symptoms in the area of the excised tarsal coalition. If the adult patient is going to undergo attempted resection of a tarsal coalition, he or she should understand that arthrodesis might eventually be necessary to treat the condition and diminish the symptom complex.1

The articular involvement, or the joints affected by the tarsal coalition, is likely the most important factor when one is considering the surgical options for the treatment of a tarsal coalition. Tarsal coalitions may be divided into those that are extra-articular (i.e., those occurring outside normal joints) and those that are intra-articular (i.e., those occurring within normal joints). The most common extra-articular tarsal coalition is the calcaneonavicular bar since there is not a normal articulation between the calcaneus and the navicular. Conversely, the most common intra-articular tarsal coalition is the middle facet talocalcaneal coalition since this abnormal union directly disrupts the subtalar joint.

Extra-articular coalitions are generally more responsive to resection because their excision does not destroy or alter the existing tarsal joint articulations. In contrast, intra-articular coalitions are generally less amenable to resection because their excision alters an already abnormal tarsal joint.1

The presence or absence of arthritic or adaptive changes in the joints surrounding a tarsal coalition has a clinically significant impact on the selection of a surgical treatment plan. These changes are believed to result from the restricted motion and altered biomechanics created by the tarsal coalition, and are therefore termed secondary arthritic or adaptive changes.

Many of these changes classically occur in patients with tarsal coalitions. For example, talonavicular joint arthritis is a secondary change, which occasionally occurs with a middle facet talocalcaneal joint coalition. Narrowing of joint spaces, joint lipping or osteophyte formation and adaptive changes in osseous structures and joints are all frequent secondary arthritic or adaptive changes that may be associated with a tarsal coalition. Intuitively, the greater the severity of the secondary arthritic or adaptive changes present with a tarsal coalition, the more difficult the surgical procedure will be for correction of that coalition.

Further, with more secondary arthritic and/or adaptive changes, the tarsal area will be less responsive to simple resection of the tarsal coalition. Secondary adaptive changes, which are deemed non-arthritic, are less problematic and have less of an effect on the foot after surgical resection of the coalition. Resection of a tarsal coalition in the presence of significant secondary arthritic changes could necessitate further biomechanical adjustment in an already mechanically compensated foot. This generally results in further aggravation of any existing symptom complex. Therefore, when severe secondary arthritic or adaptive changes are associated with a tarsal coalition, arthrodesis is usually considered the operation of choice.1

This categorization is somewhat antiquated as coalitions are rarely, if ever, entirely cartilaginous or fibrous in nature. Therefore, a tarsal coalition is better termed as either complete (i.e., an entirely osseous coalition) or incomplete (i.e., a fibrocartilaginous coalition). For extra-articular coalitions, such as the calcaneonavicular bar, the tissue composition and size of the coalition seem to have little bearing on the ultimate surgical approach. However, this is not the case for an intra-articular tarsal coalition such as the middle facet talocalcaneal coalition.

Researchers have made attempts using preoperative CT scans to determine whether the size of a talocalcaneal coalition affects the result obtained with resection. Wilde and colleagues examined 20 feet in 17 patients, all less than 16 years of age and each undergoing resection of a talocalcaneal coalition.10 These investigators reported excellent or good results in 10 (50 percent) feet in patients in whom the preoperative coronal views on the CT scan showed less than 50 percent involvement of the posterior facet of the subtalar joint. These patients also had less than 16 degrees of heel valgus and no radiographic signs of arthritis of the posterior facet of the talocalcaneal joint.

In the 10 feet with fair or poor results, coronal CT sections showed greater than 50 percent involvement of the posterior facet.10 The patients also had greater than 16 degrees of heel valgus and radiographic changes of the posterior facet consistent with arthritis. These investigators concluded that one could obtain excellent or good results if the coalition involved less than 50 percent of the joint, but fair or poor results occurred with attempts at resection of larger coalitions.

Similarly, Comfort and Johnson found that the clinical results obtained with resection correlated well with the size of the coalition.11 These authors reviewed a series of 20 feet undergoing resection of talocalcaneal coalitions (16 patients). There were preoperative CT scans for 17 feet. The average patient age was 14.2 years and the mean follow-up was 2.4 years postoperatively. Unlike Wilde and associates, these authors evaluated all three facets of the subtalar joint and not just the posterior facet. They found 77 percent excellent or good results when the coalition involved less than one third of the entire subtalar joint as measured on a coronal CT view.

Therefore, the size of the tarsal coalition seems to have relevance in the choice of a surgical plan for patients with intra-articular tarsal coalitions. However, researchers have not determined a threshold size that precludes resection.

Other Pertinent Surgical Insights

The patient and/or parents of the patient should be involved in the selection of an appropriate surgical treatment plan. If the surgical plan one chooses is a resection procedure, review the potential need for future arthrodesis with the patient and/or parents prior to surgery. In the best of circumstances, a percentage of patients undergoing a resection procedure will fail to improve and will require an arthrodesis approach.

Typically, the arthrodesis approaches include a single arthrodesis procedure, such as a subtalar joint arthrodesis for a middle facet talocalcaneal coalition, or a triple arthrodesis for more advanced deformities, such as a calcaneonavicular coalition or talocalcaneal coalition in a patient with severe secondary arthritic changes. When performing an arthrodesis approach, the position of the arthrodesis is critical to the success of the procedure. Severe heel valgus is often associated with a tarsal coalition. One must address and correct this during the fusion procedure.

When the surgeon performs resection of a tarsal coalition, following several principles will maximize success. First, approach the coalition as directly as possible. Second, perform a generous resection of the tarsal coalition. Third, if one inserts interpositional materials into the defect, they should be as inert as possible and minimize scar tissue formation. Fourth, perform early mobilization of the resected area postoperatively. Finally, one will need to address any associated pes planovalgus deformity either simultaneously or postoperatively with conservative measures or at a second surgical sitting.

The two most common tarsal coalitions are the calcaneonavicular bar and the middle facet talocalcaneal bridge.1 Surgeons have managed both with surgical resection and fusion approaches. Slomann first described the resection of the calcaneonavicular coalition in 1921 and Badgley further elucidated the procedure in 1927.12,13 Authors have referred to the traditional approach as an extensor digitorum brevis arthroplasty. This involves excision of the calcaneonavicular bar through a dorsolateral midfoot Ollier’s incision with interposition of the extensor digitorum muscle belly into the defect. Over the years, the procedure has remained essentially unchanged with suggested modifications centering primarily on the interpositional material.

The procedure has worked quite well for the calcaneonavicular coalition with reported success rates averaging about 80 percent.1 Recently, Lui reported using arthroscopy to resect a calcaneonavicular coalition.14 He described his technique of using a 2.7 mm, 30-degree arthroscope and two arthroscopic portals to shave the coalition. However, Lui did not report any results.

Although somewhat more controversial, surgeons have also successfully resected the middle facet talocalcaneal coalition. A medial longitudinal incision approach over the sustentaculum tali allows direct exposure of the middle facet talocalcaneal coalition. Intraoperative fluoroscopy and passing guide pins from the sinus tarsi medial wards help to localize the coalition and confirm its dimensions. Typically, one retracts the tibialis posterior and flexor digitorum longus tendons dorsally, and retracts the neurovascular bundle and flexor hallucis longus tendons inferiorly. After exposing the coalition, gently resect it.

Debate continues as to whether interpositional material is necessary and what the best material would be. Bone wax, fat grafts, combinations of bone wax and fat grafts and split tendons (e.g., split flexor hallucis longus tendon) are suggested interpositional options. Authors have reported good results with no interpositional material at all or with the insertion of a subtalar arthroereisis implant.15 The goal of the implant approach is to keep the resected space open by holding the foot in a more supinated position. There is no current evidence to suggest that failure of talocalcaneal coalition resection is related to the interpositional material used or lack thereof.

On the other hand, several authors have suggested that failure of talocalcaneal coalition resection is due to the degree of hindfoot valgus present. Wilde and associates found that more than 16 degrees of heel valgus correlated with a poor outcome after resection.10 Luhmann and Schoenecker found no problems with 16 degrees of heel valgus but did find poorer outcomes with resection of talocalcaneal coalitions in patients with more than 21 degrees of heel valgus.16 These authors suggested either a medializing calcaneal osteotomy or a lateral column lengthening along with resection of a talocalcaneal coalition associated with severe hindfoot valgus.

More recently, Kernbach and colleagues advocated a single stage approach with resection of the talocalcaneal coalition and flatfoot reconstruction.17 They reported good results in six cases in three patients.

When a tarsal coalition is associated with severe hindfoot valgus, one must address the valgus either conservatively or surgically if the coalition is going to undergoing resection. Whether this should occur in one stage or in two stages is still open to debate. Overall, the success rates for resection of talocalcaneal coalitions reportedly average about 80 percent.1 Although the success rate of talocalcaneal coalition resection seems to parallel the success rate of calcaneonavicular coalition resection, it is generally considered to be less successful. As with talocalcaneal coalition resection, the primary improvement is a noted reduction in pain.

In contrast, with a calcaneonavicular coalition resection, there is a noted reduction in pain with generally greater functional improvement and motion. A full return of joint motion following coalition resection does not appear to be necessary for a successful result.1,18

In Summary

Tarsal coalitions remain a challenging pedal condition to manage successfully. Knowledge of the signs and symptoms of tarsal coalition along with a vigilant index of suspicion for the potential presence of a tarsal coalition are necessary to identify and diagnose the entity. Conservative treatment for a tarsal coalition is generally oriented toward rest, immobilization, offloading, biomechanical control and anti-inflammatory modalities.

When conservative treatment fails or is superfluous, surgery is often indicated. The criteria for successful surgical intervention and deciding between resection approaches and arthrodesis are slowly becoming better elucidated. Currently, the evidence suggests that the most important parameters to consider when developing a surgical treatment plan are patient age, articular involvement, the presence or absence of secondary arthritic and adaptive changes, the size of the coalition and the severity of any hindfoot valgus.

Dr. Downey is the Chief of the Division of Podiatric Surgery at Penn Presbyterian Medical Center in Philadelphia. He is also a Senior Faculty Member of the Podiatry Institute. Dr. Downey is also a Fellow of the American College of Foot and Ankle Surgeons.